Parallel programming in Meadow.OS is essentially the same as any other .NET enabled platform. Meadow fully supports System.Threading and System.Threading.Tasks as well as the underlying Task Parallel Library methods.
For example code using these technologies, see the following samples in the Meadow.Core.Samples repo:
BeginInvokeOnMainThread
The MeadowOS class has a BeginInvokeOnMainThread method that enables code to be put into a queue to be executed on the main thread:
Task.Run(() => {
MeadowOS.BeginInvokeOnMainThread(() => {
...
});
});